ultrasonic thickness gauges - ndt thickness

The thickness of materials cannot always be determined by direct measurement as access to both sides is not always possible. The effects of corrosion and erosion at the back of a metal panel may reduce its thickness significantly yet not affect the front surface. Pipelines, for example, may have been eroded by the flow of material inside. Machined or cast items may have thin walls that cannot be determined by callipers or other non-destructive tests.